With respect to earlier known apparatus and arrangements for anaesthetising a patient to a chosen depth of anaesthesia, it is normal to divide such states into three different categories, depending on the degree of consciousness of the patient, namely:                general anaesthesia, a state in which the patient is rendered unconscious artificially and kept within adapted degrees or levels of unconsciousness (depth of anaesthesia);        regional anaesthesia, a state of insensitivity in the spine of a patient; and        local anaesthesia a state which is mainly applicable to minor surgery or treatment.The patients are conscious in the latter two categories.        
The present invention is adapted for application in the general anaesthesia category.
This category includes two different groups of anaesthesia, namely inhalation anaesthesia and total intravenous anaesthesia.
There is used within the first anaesthesia group, inhalation anaesthesia, a lung ventilator that includes vaporiser equipment for anaesthesia inducing pharmaceutical, said lung ventilator creating conditions for the insufflation and expiration of air or air mixed with gaseous oxygen, which is mixed, in turn with anaesthesia inducing gases.
Although apparatus designed for inhalation anaesthesia have found wide use, they require the appropriation of very complicated equipment, partly to enable the insufflation and expiration phases to be controlled and partly to administer the supply of gaseous pharmaceutical, and also to evaluate patient related criteria and to regulate said criteria when necessary.
Thus, it is likely that anaesthesia inducing gases will accompany the expiration gas in each expiration phase and consequently it is necessary to remove these gases from every enclosed space, such as the operating theatre, effectively and at short intervals. In addition, the equipment must, of course, be gas tight in general.
It is also known in the case of such practice to assemble an inhalation anaesthesia related system within respective clinics with the aid of different apparatus obtained from different manufacturers and designed for different purposes.
It is also known to appropriate a single system from a single manufacturer. Such systems, however, are highly complicated and the component parts of such systems make the equipment extremely heavy. It is also found that such a system is space consuming and expensive and that the necessary inspections for possible leakage are very difficult to carry out.
The present invention relates to and includes an arrangement within the second anaesthesia group, i.e. total intravenous anaesthesia, wherein a volume of occurring or existing anaesthesia-inducing pharmaceutical in liquid phase is allowed to infuse per unit of time into the bloodstream of the living creature or patient.
It is necessary in this case to use a lung ventilator and an infusion unit which, with the aid of a control unit, is able to induce a given depth of anaesthesia in the patient and to keep the patient within adapted levels of said chosen depth of anaesthesia.
It is known in this respect to use a number of apparatus taken from different manufacturers and to assemble these apparatus into a system or an arrangement. In order to induce a given depth of anaesthesia in a patient, each such system requires the use of a number of apparatus and measuring devices which function to enable a number of important patient criteria to be evaluated and to enable the well-being of the patient to be controlled. These criteria have normally been presented as instantaneous values and/or curves on the display surface of each apparatus.
Criteria that concern the well-keeping/treatment of a patient are designated therapeutic criteria and are detected/sensed, regulated and evaluated in one or more therapeutic units.
Criteria that relate to patient diagnosis or patient supervision are referred to as diagnostic criteria and are sensed/detected and evaluated in one or more diagnostic units.
Some significant units and criteria in the present context have been listed in FIG. 1, in which reference sign A identifies a lung ventilator and an associated control unit; B identifies an infusion unit and associated control unit for making necessary adjustments to the volume of anaesthesia inducing pharmaceutical per unit of time; C identifies a unit which senses/detects prevailing air pressure, i.e. the air pressure in the mouth of the patient; D identifies a unit which evaluates the flow of air into the patient's lungs and, when necessary, also out of the lungs; E identifies a unit which evaluates the CO2-content and the O2-content of the air entering the lungs, and when necessary also the expiration air; F identifies a unit for evaluating ECG-values; G identifies a unit that evaluates blood pressure values NIBP; H identifies a unit for establishing oxygen saturation in the blood (SpO2); I identifies a unit which evaluates the degree of consciousness of the patient (the depth of anaesthesia) via sensed brain activity (the BIS-values); and J identifies a unit which evaluates PEEP-value.
It is known in systems of this nature adapted for total intravenous anaesthesia to allow a number of the criteria given under A–J above to be interconnected and combined in a common unit.
For instance, it is known to combine the units for criteria C and J and for A, D and E respectively into a single unit. The criterion B and combinations of criteria F, G and H normally require separately operated and individual units.
Known technology teaches the use of the infusion unit B and the lung ventilator A as separate units. These units are used to control the well-being of the patient and therefore include a number of therapeutic units.
Other equipment and units are primarily designed to produce instantaneous values or curves for other relevant patient-related criteria and include a number of diagnostic units.
By instantaneous values shall be understood measured values that can be evaluated instantaneously in the true meaning of the word, and also the formation of mean values of a selected number of sensed/detected instantaneous measurement values.
In the case of so-called multi-parameter monitors, it is known to co-ordinate the evaluated instantaneous values and the values for presentation of time-related graphs for selected relevant criteria and to show these graphs on a display surface.